(1) Field of the Invention
The present invention relates to solutions for use in reducing nitrogen volatilization comprising N-(n-butyl)-thiophosphoric triamide (NBPT) dissolved in one or more N-substituted morpholines or mixtures thereof, to methods of making fertilizers using these solutions, and to the resultant fertilizers. The solutions also find utility in reduction of odors from animal wastes.
(2) Description of the Prior Art
Urea is a commonly used nitrogen source in agriculture which is subject to degradation in the soil by action of the enzyme urease. This degradation leads to loss of nitrogen as ammonia in a process known as volatilization. A number of approaches have been tried to protect urea from volatile nitrogen loses including the use of metal inhibitors such as copper salts, or zinc salts, boric acid salts (borates), or sulfur coatings; however; the most effective method is the use of an organic urease inhibitor.
N-(n-butyl)-thiophosphoric triamide (NBPT) is a known urease inhibitor described by (Kolc et. al. U.S. Pat. No. 4,530,714). The compound is a waxy solid with poor water solubility making it difficult to coat urea and achieve adhesion of the compound. The compound undergoes hydrolysis and is thermally unstable. The 714 patent describes the formation of a number of phosphoric or thiophosphoric triamides including N-(diaminothiophosphinyl)morpholine (N-morpholinyl)thiophosphoric triamide), N-(diaminophosphinyl)morpholine.
In the soil, NBPT converts to the phosphoric triamide form (oxon analog) which is the more potent but much more unstable inhibitor (McCarthy, G. W., Bremner, J. M., and Chai, H. S. “Effect of N-(n-butyl)-thiophosphoric triamide on the hydrolysis of urea by plant, microbial and soil urease.” Biology and Fertility of Soils Volume 8 Pages 123-127, 1989). For commercial use it is desirable to protect the sulfur atom of the thiophosphoric triamide structure of NBPT until it reaches the soil.
The 714 patent describes the mixing of NBPT with organic solvents (acetone, disobutylketone, methanol, ethanol, 2-propanol, ether (diethyl), toluene, methylene chloride) to distribute the compound into the soil in an effective concentration range which can be anywhere from 5 ppm to 100 ppm depending upon the soil. The organic solvents described by the 714 patent are either too flammable for use or pose significant health risks to be considered suitable for coating urea granules.
In an alternate method, the 714 patent indicates that NBPT can be mixed with solids such as gypsum or clay to distribute the compound into the soil in an effective concentration.
Omilinsky et. al. (U.S. Pat. No. 5,698,003) describes the dissolution of NBPT with a glycol such as propylene glycol or ethylene glycol and esters of glycols. Glycols are compounds with adjacent alcohol groups in the chemical structure. The glycol solvent may contain a co-solvent liquid amide such as N-methyl-2-pyrrolidine and potentially a surfactant or dispersing agent such as polyethylene glycol or esters of polyethylene glycol (polyether alcohols). Other liquid amides disclosed by the teachings of Omilinsky (714 patent) include: formamide, N—N-dimethyl formamide, N,N-dimethyl acetamide, N-butyl N-phenylacetamide. In another group of compounds disclosed as co-solvents by Omilinsky et. al., include intramolecular amides which are heterocyclic structures with a nitrogen atom and oxygen atom on the adjacent carbon such as: N-alkylpyrrolidones. The N-alkylpyyrolidones disclosed in the teaching of Omilinsky et. al. are: N-methyl-2-pyyrolidone (preferred), N-octyl-2-pyrrolidone, and N-dodecyl-2-pyrrolidone. Omilinsky et. al. indicates that esters of glycerol (a triol) may be used as the base solvent. Urea granules containing NBPT are prepared by mixing the urea granules with the NBPT dissolution solvent. Omilinsky et. al. teach that a drying agent such as clay or gypsum may be added to the compositions in the event that a product with excessive wetness is obtained.
Weston et al. (U.S. Pat. No. 5,352,265 and U.S. Pat. No. 5,364,438) teach the dissolution of NBPT in liquid amides such as 2-pyrrolidone or N-alkyl-2-pyrrolidones such as N-methyl-2-pyrrolidone to prepare both solid urea formulations (265 patent) or liquid formulations (438 patent).
Hojjatie et al. (US 2006/0185411) teach the use of a number of sulfur salts of calcium or magnesium (calcium polysulfide, thiosulfate, and magnesium thiosulfate) as urease inhibitors to prepare granular or liquid urea compositions.
Quin (US 2004/0163434) teaches the formation of sulfur coated urea which may contain the urease inhibitor NBPT supplied from a proprietary liquid formulation sold as Agrotain® and distributed by Koch Agronomic Services, Kansas, USA.
Sutton et al. (U.S. Pat. No. 5,247,689) teach the formation of a liquid fertilizer that includes urease inhibitors such as NBPT and nitrification inhibitors such as dicyandiamide in aqueous mixtures of urea ammonium polyphosphate, ammonium thiosulfate and potentially other plant growth improving compounds.
Sutton (US 2007/0295047) teaches the formation of a solid fertilizer comprised of urea and a urea-formaldehyde polymer which may additionally include a urease inhibitor such as NBPT.
Sutton et al. (U.S. Pat. No. 8,425,649) describes a fertilizer additive composed of urea, a urea-formaldehyde polymer and NBPT dissolved in an N-alkyl-2-pyrrolidone.
Hamad et al. (US 2007/0077428) suggests the formation of odor inhibiting fibers (diapers) comprised of a cellulosic fiber and an odor-inhibiting formulation. The odor inhibiting formulation is comprised of an odor inhibiting agent dissolved in hydrophilic or hydrophobic solvent and mixtures of hydrophobic and hydrophilic solvents. The hydrophilic solvents could include amino alcohols such as ethanolamine and diethanolamine. Acids may be added to the odor-inhibiting fiber formulations to neutralize ammonia which may be formed by breakdown of urea. Hamad et. al. (7428 patent) suggests that urease inhibitors such as NBPT may be included in the odor-inhibiting formulation.
Sun et al. (U.S. Pat. No. 6,852,904) suggests the formation of odor controlling cellulosic fibers such as diapers or medical absorbent garments in which a carboxylic acid or partially neutralized carboxylic acid are employed to form the odor-inhibited cellulosic product. The odor-inhibiting formulation may include a transition metal as a hydroxide or oxide which may be used to partially neutralize the carboxylic acid groups.
Dutkiewiez (US 2006/0020029567) teach the formation of odor control formulations using phosphoric triamides including N-(diaminophosphinyl)morpholine, N-(diaminothiophosphinyl)morpholine, N-(diaminophosphinylthiomorpholine), and N-(diaminothiophosphinyl)thiomorpholine for the purpose of odor control. The odor treatments are applied to cellulosic fibers or materials containing animal wastes. Water is used as the NBPT solvent in one example [0261] and methanol in another example [0276] in the teachings of Dutkiewiez.
Cigler (WO 2008/000196) teaches the formation of a solvent system for thiophosphoric triamide solutions comprised of one or more glycol ethers which may optionally contain substances to improve the stability of the thiophosphoric triamde. Examples of stabilizing agents include polyvinylpyyrolidone, N-methylpyrrolidone as crystallization inhibitors. Examples of glycolethers suited to the teachings are diethyleneglycolmonomethylether, dipropyleneglycolether, monomethylether and triethyleneglycolmonomethylether.
Whitehurst et al. (U.S. Pat. No. 8,163,058) teach the formation of fertilizer materials such as granular urea or liquid urea formulations in which the urea is treated with a solution containing NBPT which has been dissolved in an amino alcohol such as diethanolamine, triethanolamine, diisopropanolamine, etc. All carbon chains attached to the nitrogen atom in the solvent system described Whitehurst et. al. contain an alcohol group (058 patent).
Whitehurst et al. (U.S. Pat. No. 8,048,189) teach the formation of a solution of NBPT in a buffered mixture composed of the reaction product of an amino alcohol with a carboxylic acid up to 6 carbons in length.
Whitehurst et al. (U.S. Pat. No. 8,133,294) teaches the formation of various urea containing fertilizers from the buffered mixture of the reaction product of an amino alcohol and a carboxylic acid up to 6 carbons in length. Whitehurst et. al. (U.S. Pat. No. 8,048,189) note that the stability of NBPT is affected by pH when water is present and it is undesirable to formulate a mixture with a pH below 7. All carbon chains attached to the nitrogen atom possess an alcohol group in the amino alcohols used to prepare buffered solvents for NBPT in the teachings of Whitehurst et al. (189 and 294 patents).
Whitehurst et. al. (co-pending U.S. application Ser. No. 13/507,848) describes the use of N-alkyl, N,N-dialkyl amino alcohols and ethers of N-alkyl substituted amino alcohols as solvents for NBPT. These compounds can broadly be described as alkyl substituted amino alcohols (ASAA). The NBPT containing solutions in ASAA can have their pH adjusted with a carboxylic acid. Whitehurst et. al. indicated that the solutions of NBPT in ASAA could have greater protection against crystallization of NBPT at low temperature.
NBPT is synthesized by a reaction process (Kolc et. al 714 patent) that results in the formation of ammonium chloride. This acidic material is often present in commercial NBPT along with ammonia left over from the synthetic process. Huttenboch et. al. (US 2008/0287709) teach the use of apolar amines to remove acids from reaction mixtures including reaction mixtures from the synthesis of NBPT. The apolar amines used to remove acids from NBPT reaction mixtures include N-alkylmorpholines wherein the alkyl group could possess up to 5 carbons; such as N-methyl, N-ethyl, N-propyl, N-butyl, N-pentyl-morpholines. Branched chains of 3, and 4 carbon N-alkylmorpholines are indicated as apolar amines suited to removing acids from NBPT reaction mixtures. Many of these N-alkylmorpholines have low flash points and have strong amine odors potentially limiting their use as solvents for NBPT when preparing granular urea formulations, and could potentially be significant volatile organic carbon emitters in fertilizer formulations.
Urea is a high nitrogen analysis material which is often desirable as a starting material for making additional fertilizer products providing phosphorus or potassium as primary nutrients, calcium, magnesium or sulfur as secondary nutrients or micronutrients such as boron, copper, iron, manganese, molybdenum and zinc.
Whitehurst et al. (U.S. Pat. No. 6,030,659) teaches the formation of phosphate coated urea by first reacting urea with an acid then adding an apatite mineral phosphate source to the surface. Reaction of phosphoric acid while on the urea surface with the apatite mineral is expected to solubilize the apatite mineral to provide available phosphate. It is expected that the acidified coating would help to reduce volatile nitrogen losses from urea.
Whitehurst et al. (U.S. Pat. No. 6,830,603) describes a coating methodology wherein boron containing urease inhibitor compositions may be used to add additional nutrients such as phosphate, potassium, etc. The coating of urea with other materials is known and the references in Whitehurst et al. (603 patent) provides a partial summary of prior art in the area. The inhibitors and binders taught in the 603 patent are aqueous mixtures that include ethanolamine borates, diethanolamine borates or triethanolamine borates and mixtures of these.
Commercial products containing aqueous ethanolamine borates or triethanolamine borates are distributed under the trade name of Arborite® by Encee Chemical Sales, North Carolina, USA. The product is further identified by a binder number for separation of the different mixtures available.
Urea is a common component of animal wastes (manures, green manures, animal bedding materials contaminated with urea, etc.). These animal wastes release ammonia as they decompose due to the action of the enzyme urease. Kolc et. al. (U.S. Pat. No. 4,517,003) disclosed the use of N-acylphosphoric triamides as urease and/or nitrification inhibitors. Kolc et al. (003 patent) include manures in the fertilizers which may be protected from volatile ammonia loss by using a phosphoric triamide. The urease/nitrification inhibitor may be distributed in either liquid form (dissolved in alcohols or halogenated solvents) or in solid form (mixed with clays, vermiculite, gypsum e.g.) to distribute the phosphoric triamide onto a fertilizer (003 patent).
Weissemeier et al. (U.S. Pat. No. 8,075,659) describe the use of urease inhibited fertilizer formulations in which two phosphoric triamide urease inhibitors are used. The phosphoric triamides may be present in the thiophosphoric triamide form. Liquid manures may be treated with the combination of urease inhibitors.
Sheets (U.S. Pat. No. 7,422,680) teach the use of a urease inhibitor such as NBPT in the pretreatment of animal wastes to prevent ammonia release when making fertilizers from animal wastes.
Aylen et al. (U.S. Pat. No. 7,434,540) teach the use of clay based animal bedding material as an absorbent to reduce ammonia levels, odor, microorganisms and insects in animal stalls. The clay based absorbent may contain NBPT as a urease inhibitor.
The use of NBPT or other phosphoric and/or thiophosphoric triamides requires a dispersal mechanism and most of the patents previously identified deal with materials which can be used to disperse NBPT, other thiophosphoric triamides, and phosphoric triamides in liquids or solids. The teachings of the prior art indicate that liquid dispersal agents (solvents) are desired which are safe to handle, easily mix with water, that are stable under somewhat broad temperature conditions and protect the compounds from degradation to unstable forms that are less active as urease inhibitors. A desirable feature for the solvent systems for NBPT is their ability to keep the NBPT dissolved under low temperature conditions. This is made somewhat difficult by the endothermic heat of solution of NBPT and therefore its tendency to crystallize from concentrated solutions at low temperature.
Morpholine is a chemical compound with low molecular weight, which has been used, in many commercial applications. The basic structure of morpholine is that of a six-atom heterocyclic ring composed of an oxygen atom and a nitrogen atom at opposite ends of the heterocyclic ring. The nitrogen and oxygen atom are separated by 2 carbon atoms.
The nitrogen atom of the morpholine structure may be converted into a tertiary nitrogen atom by addition of an alkyl group such as a methyl, ethyl, propyl (isopropyl or n-propyl) or butyl groups (isobutyl, secbutyl, tert-butyl, n-butyl) groups. The alkyl substitutions could potentially contain unsaturated carbon chains. Additionally, the nitrogen atom can be reacted with ethylene oxide, propylene oxide, or butylene oxide to create alkyl structures attached to the nitrogen atom that further possess a hydroxyl group. The nitrogen atom of morpholine can be reacted to form an amide structure such as that of N-formyl morpholine, N-acetyl morpholine, N-propyl morpholine and other 3 or 4 carbon structures in which the N atom of the amide is contributed by morpholine.